Drum solenoid interface for Tactile Metronome

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The Maker Shed is brought to you by Maker Media, the makers of MAKE Magazine, the Maker Faire, and much more.

Launched originally as a source for back issues of MAKE Magazine, the Maker Shed expanded rapidly to meet the demand for 'projects in a box,' otherwise known as kits. Now we have a little bit of everything for makers, crafters, and budding scientists, from Arduinos to sock monkeys to chemistry sets .

If you stopped by our table at the Maker Faire, you got to play around with our big drum demo of the Tactile Metronome. Lots of people had questions about how we drove the solenoid for the drum striker, so we decided to write it up once we got back home.
For the drum striker, we used an electromagnetic solenoid, which consists of a coil of wire wound around a movable metal core. When current is sent through the coil, the metal core moves a short distance. Unfortunately, the pins on a microcontroller are relatively weak, meaning that they can only supply 20-40 milliamps (mA) of current, compared to the 1 amp draw of our solenoid. This means that we can’t directly connect the microcontroller to the solenoid, as not enough current would be supplied. The usual solution to this drive strength problem is to use a transistor as a switch.

The Maker Shed is brought to you by Maker Media, the makers of MAKE Magazine, the Maker Faire, and much more.

Launched originally as a source for back issues of MAKE Magazine, the Maker Shed expanded rapidly to meet the demand for 'projects in a box,' otherwise known as kits. Now we have a little bit of everything for makers, crafters, and budding scientists, from Arduinos to sock monkeys to chemistry sets .

The Maker Shed is brought to you by Maker Media, the makers of MAKE Magazine, the Maker Faire, and much more.

Launched originally as a source for back issues of MAKE Magazine, the Maker Shed expanded rapidly to meet the demand for 'projects in a box,' otherwise known as kits. Now we have a little bit of everything for makers, crafters, and budding scientists, from Arduinos to sock monkeys to chemistry sets .